This invention pertains to methods and apparatus for securely engaging a module, such as a computer component, into a connector which is supported on a chassis or a main board.
The present invention is particularly useful in systems such as disk arrays and the like, but can be applied to any situation where it is desired to securely mount a component or module into a connector which is supported on or by a chassis or frame or the like. A disk array is a battery of computer memory disk drives which are mounted together within a cabinet. Disk arrays fit within a category of computer equipment known as xe2x80x9cstorage systemsxe2x80x9d because the system is used to store large amount of data. A typical use of a disk array is an Internet server which stores web site information, including content which can be accessed from the web site. It is not uncommon for a disk array to have the capacity to store several terabytes of data (a terabyte being 1000 gigabytes).
A disk array typically consists of a cabinet which houses a plurality of disk drives. The disk drives are mounted by connectors to a board or xe2x80x9cplanexe2x80x9d, which is supported by a chassis, all within the cabinet of the disk array. Depending on the location of the plane within the cabinet, the plane can be known as a xe2x80x9cmidplanexe2x80x9d (mounted towards the middle of the cabinet so that disk drives can be mounted to either side of the plane), or a xe2x80x9cback planexe2x80x9d (mounted towards the back of the cabinet so that the disk drives are only mounted to one side of the plane). The chassis can further include framework for supporting the disk drives, and to facilitate orienting the disk drive to the connectors. In this manner a disk drive can be inserted or removed from the array.
The plane further supports electrical conductors for routing power and data to and from the disk drives via the connectors. The electrical conductors are routed to a main connection, allowing a remote computer to store and retrieve data from the disk array. The connectors on the plane can be female connectors which are configured to receive male connector pins on the disk drive. Each disk drive typically has a plurality of such xe2x80x9cpinsxe2x80x9d which mate with the corresponding female connectors on the plane to allow the individual disk drives to send and receive data via the electrical conductors. In other systems, the module can have female connectors, and the panel or board to which the module is being mounted can have corresponding male pins for completing the connection. Although we use the term xe2x80x9cpinxe2x80x9d to describe the male component of the connector assembly, it is understood that the xe2x80x9cpinxe2x80x9d can in fact be a blade, a cylinder, a rectangle, or any other protruding geometry which allows it to be inserted into a female receiving connector component.
Turning briefly to FIG. 1A, a side view of a prior art connector 1 is shown in cross section. The connector 1 is mounted on the plane 2. The connector housing 1a defines a cavity 3, in which is located female connectors 4 and 5, which together form a single female connector component. Female connectors 4 and 5 are spring biased towards the center of the cavity 3 such that when a male connector pin 6, which is connected to module 7, is moved in direction xe2x80x9cAxe2x80x9d, the female connectors are pushed apart, but remain biased against the pin 6. Such biasing assures good electrical contact between the connector components.
To maintain the module securely seated in its receptacle within the frame of the disk array, a latch can be provided which secures the module to the chassis or frame. With reference to FIG. 2, a prior art disk array 10 is shown. The disk array comprises a cabinet 11 in which a chassis or frame 12 is disposed. The chassis 12 comprises side rails 23, a top rail 22, and intermediate vertical rails 15 and 17, which when assembled form openings 13 in which a disk drive, such as disk drive 14, can be inserted. The disk drives mate to connectors 1 which are mounted to a plane 25, visible through the openings formed by the chassis members. Disk drive 14 is secured within the opening 13, and is securely seated to connector 1, via the latch 20. Turning now to FIG. 3, a left side sectional view of the upper left opening 13 of the prior art disk array 10 of FIG. 2 is shown. As can be seen, intermediate chassis rail 15 has an anchor point 21 which is configured to be engaged by the latch 20 of FIG. 2.
Turning now to FIG. 4, a perspective view of the disk drive 14 of FIG. 2 is shown in more detail. FIG. 4 depicts the prior art latch 20 and its method of engagement with intermediate chassis rail 15. To secure the disk drive 14 to the midplane (25 of FIG. 3), the far end 29 of the latch 20 is moved in the direction of arrow xe2x80x9cBxe2x80x9d until handle catch portion 31 engages the disk catch portion 32 to maintain the latch 20 in the secured position. The latch assembly is shown in top view in FIG. 5. The latch 20 of FIG. 5 includes a leveraging edge 30 which engages flange 33, which acts as an anchor point for the latch. As can be seen, when latch 20 engages anchor point 33 and is moved in direction xe2x80x9cBxe2x80x9d, the latch 20 pivots about pivot point 28 and the disk drive 14 is pulled in direction xe2x80x9cAxe2x80x9d into the opening 13. Latch 20 is moved in direction xe2x80x9cBxe2x80x9d until the latch is secured by the catch 32. Catch 32 can comprise a spring-release catch having moveable part 34 which moves in direction xe2x80x9cCxe2x80x9d to allow catch pin 31 on latch 20 to move past the catch pin. The latch is secured in the xe2x80x9clockedxe2x80x9d position when the catch pin moves back to its biased position. By pulling the latch in the direction opposite to xe2x80x9cBxe2x80x9d the catch pin is pushed aside, allowing the disk drive to be freed from the anchor point 33.
In designing a connector system for an electronic module, two primary considerations are taken into account. The first is to ensure that the connector pin (6 of FIG. 1A) is sufficiently engaged by the connector contacts 4 and 5. This is necessary for the obvious reason that if no contact is made, data and power cannot be transferred to and from the disk drive. The second consideration is to ensure that excessive force is not applied to the connector system when the connection is made and the module is seated. This is necessary since a force exerted on the midplane can lead to premature failure of the midplane, failure of solder connections, and damage to the connector components. Further, forces exerted on components within the module by the module connectors can lead to failure of these components as well. As shown in FIG. 1A, the first objective of ensuring a connection between the contacts is achieved by designing the connector pins 6 and the contacts 4 and 5 such that there is a reserve wipe distance, drw, i.e., a distance over which the pin 6 travels after it has made initial contact with the connector contacts 4 and 5. The second objective of avoiding an excessive force on the midplane is achieved by designing the connector assembly such that there is a design gap, ddg, between the connector housing 1a and the disk drive connector housing 7.
However, in production units the actual wipe distance and the actual gap distance can vary from the design wipe distance and the design gap distance. This variance is due to tolerances in the various components in the chassis, the plane and the module. These tolerances can be due to sheet metal tolerances, printed circuit board (e.g., midplane) tolerances, press-in standoff tolerances, and connector tolerances, to name just a few. The cumulative effect of these tolerances is expressed by the equation
tolsys=(tol12+tol22+tol32+ . . . +toln2)xc2xd, 
where tolsys is the cumulative tolerance of the system, and tol1xe2x88x92n represent the various tolerances of the components. If the system tolerance indicates that the actual gap distance might be reduced to zero, then the situation shown in FIG. 1B can occur, wherein the module connector housing 7 butts up against the connector housing 1a. In this instance an undesirable force can be applied to the midplane 2 by a force in the direction xe2x80x9cAxe2x80x9d exerted by the latch (20 of FIGS. 2 and 4). Likewise, if the system tolerance indicates that the actual wipe distance might be reduced to zero or less, then the pin 6 of FIG. 1A can fail to mate with the connectors 4 and 5, which is obviously undesirable.
One solution to overcome the problem of cumulative tolerances is to reduce the various tolerances which contribute to the overall system tolerance. However, this is not always practical due to machining and fabrication limitations, and can be difficult to implement since components of the system can be manufactured by a variety of different manufacturers. Another solution is to increase the length of the connector pin 6. This will insure that a wipe distance is always achieved while allowing room for a design gap to be maintained. However, this is not practical for two reasons. First, an overly long connector pin can contact the midplane, exerting an undesirable force on the midplane and possibly allowing the connector pin to bend and damage the contacts 4 and 5. Second, the dimensions of many connector components are established by industry standards. These standards are typically a compromise to achieve the best solution to a variety of design considerations. Changing these standards can be a long and arduous process, and can exacerbate the other problems that are addressed by the standard. Further, changing an industry standard will result in incompatible units being present in the field (old standard equipment and new standard equipment), and the cost to change production lines to meet the new standard can be considerable.
What is needed then is a method and apparatus for allowing an electronic module to be securely seated in a connector, such that electrical contact between the connector components is achieved and maintained, while avoiding excessive forces on the connector components and their associated circuit boards.
The invention includes methods and apparatus for securing a first electrical connector mounted to an electronic module to a second electrical connector supported by a support structure. The support structure can comprise an electrical board supported by a chassis. The invention facilitates mating of the first and second electrical connectors in an electrically conductive manner, while at the same time helping to reduce undue stress on the connector components.
One embodiment of the apparatus includes a latch with a first end configured to engage the support structure, and a lever portion configured to exert a force on the electronic module when the lever portion is in a first xe2x80x9clockedxe2x80x9d position. This force allows the electrical connector on the module to be urged towards the electrical connector on the electrical board, and mate therewith. The apparatus also has a compliant member configured to bias the lever portion away from the first xe2x80x9clockedxe2x80x9d position, and a catch configured to secure the latch in the locked position. In this manner, the compliant member applies a biasing force to the latch, which force is transmitted to the module. The biasing force has the effect of reducing the force applied to the connectors by the latch, thereby reducing the risk of overstressing of the connector components.
In one embodiment of the apparatus, the compliant member can comprise a spring disposed between the support structure and the first end of the latch which engages the support structure. In another embodiment the compliant member can be integral with the latch, such that the compliant member comprises a segment of the lever portion of the latch. In this embodiment, the segment of the lever portion of the latch can be fabricated from a resilient material configured to orient the lever portion in a normal position when the lever portion of the latch is unstressed. When the lever portion is moved from the normal position to the first or xe2x80x9clockedxe2x80x9d position, the resilient segment of the lever portion is stressed to bias the lever portion away from the locked position and towards the normal position. This has the effect of applying the biasing force to the connectors, as described above.
In one embodiment of a method in accordance with the present invention a first force is applied to the electronic module to urge the electronic module towards the support structure from a first position to a second position, to thereby cause the first electrical connector on the module to mate in an electrically conductive manner with the second electrical connector on the support structure. Thereafter a second force is applied to the electronic module to maintain the electronic module in the second, mated, position. The second force is selected to be not greater than a predetermined force, and is preferably selected to be a force which will not cause damage to, the first connector, the second connector, or the board. The second force can be produced by applying a biasing force to the module using apparatus in accordance with the present invention. The method can further include providing a compliant member configured to exert the second force on the electronic module when the compliant member is reconfigured from a normal position to a biased position. Further, the method can include providing a catch to hold the compliant member in the second position.